I advise you to select a WM based on Wayland because it now reached a sufficient maturity and Xorg can safely be remembered as historical. I personally use sway which is an implementation of i3wm for wayland. You will have an experience similar to what appears in your screenshot.
There are a lot of status bars for sway. I am using swaybar with i3status for the status_command. Don’t hesitate to check the alternatives, they are amazing.
All the configuration of sway happens in a config file and you can setup your keyboard preference inside. You can setup multiple layouts at the same time and specify which key binding to switch between them.
If you decide to give NixOS another try (which it deserves), the nixos config already has options to enable sway.
For the package manager, either stick with the one integrated in the distribution you choose (apt, pacman, dnf, …) or indeed use nix on top if you like the experience and its benefits.
And as a general advise, don’t hesitate to first try your choices in a VM installation, and take your time to check if it really suits your need.